Drilling fluid



chemicals thereto or by dilution with water.

United States Patent DRILLING FLUID Walter J. Weiss, Sugar Land, and Wilbur L. Hall, Bellaire, Tex., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application July 25, 1956 Serial No. 599,894

17 Claims. (Cl. 2528.5)

This invention relates to the drilling of wells through subsurface formations by means of well drilling tools. More particularly, this invention relates to a drilling operation, such as a rotary drilling operation, which involves circulation of a drilling fluid through the well bore and about the drilling bit. In a rotary drilling operation a stream of drilling fluid is continuously pumped down the drill stem to the drilling bit at the bottom of the bore hole. The stream of drilling fluid passes through or about the drilling bit and moves upwardly through the annular space between the drill stem and the well bore wall carrying with it the drilling cuttings.

In some areas, such as in the area of the Gulf Coast of Texas and Louisiana, subsurface formations known as heaving or sloughing shales are penetrated during a well drilling operation. The penetration of these formations while employing conventional aqueous or waterbase drilling fluids has been diflicult due to the mudmaking characteristics or properties of heaving shales. These shales have a tendency to disintegrate by swelling or cracking upon contact with water with the result that the walls of the bore hole become unstable or incompotent and the heaving shale material making up the walls of the bore hole becomes unstable and sloughs into the bore hole. In some instances the heaving shale material swells and sloughs or caves into the bore hole with a resulting enlargement of the bore hole or the formation of a large subterranean cavity.

In addition to the above-indicated difliculties of maintaining a true bore hole when drilling through heaving shale material with a conventional water-base drilling fluid, the resulting finely dispersed heaving shale material taken up into the drilling fluid adversely affects the viscosity characteristics of the drilling fluid because of the mud-making properties of the heaving shale. Upon continued accumulation of the dispersed finely divided heaving shale particles in the drilling fluid the viscosity of the drilling fluid increases with the result that the drilling fluid must be thinned by the addition of costly If the drilling fluid is thinned by water dilution the addition of more weighting material, such as barium sulphate (barytes), iron oxide, lead sulphide (galena) and the like is necessary in order to maintaina given mud weight.

Special drilling fluids or muds have been developed for drilling through heaving shale formations. One such drilling fluid which has been employed for' drilling through heaving shale formations is a drilling fluid containing aqueous sodium silicate. Another drilling fluid which has been proposed for use during a drilling operation while drilling through less seriously dispersing or heaving shale formations is a high pH, lime-base drilling fluid which contains lime together with quebracho, caustic soda, water, and the conventional hydratable type of drilling clay. High pH, lime-base drilling fluids, however, cannot be employed without considerable difliculty v while drilling through the more seriously heaving shale formations. Also, a high pH, lime-base drilling fluid is sensitive to salt or calcium contamination, such as contamination by calcium chloride or calcium sulphate, which leads to clay fluocculation with a resulting increase in viscosity and water loss. Although in some instances the desirable viscosity, mud Weight and water loss properties of a high pH, lime-base drilling mud can be maintained While drilling through a heaving shale formation by the addition of suitable chemicals, such as the addition of caustic soda and quebracho and the like, the continued addition of these chemicals to the drilling fluid involves considerable expense.

Accordingly it is an object of this invention to provide an improved drilling fluid suitable for drilling through troublesome shale formations of the heaving, sloughing or rapidly dispersing type.

It is another object of this invention to provide a reagent material suitable for the preparation and/or maintenance of a drilling fluid useful for drilling through troublesome shale formations of the heaving, sloughing or rapidly dispersing type.

It is another object of this invention to provide a drilling fluid which is capable of being more readily maintained at a given weight while being employed as a drilling fluid during drilling through heaving or sloughing shale formations.

It is another object of thisinvention to provide a drilling fluid which is relatively insensitive to salt (NaCl) contamination and to calcium ion contamination, such as may arise while drilling through a gypsum bed or upon encountering a high pressure 'salt water flow.

It is another object of this invention to provide a composition suitable forthe preparation of an aqueous drilling fluid which readily converts heaving shale material exposed in the well bore into a more competent material.

Yet another object of this invention is to provide a drilling fluid reagent material or admixture suitable for the preparation of an alkaline aqueous drilling fluid characterized by a relatively high dissolved barium or barium ion content.

These and other objects of this invention and how they are accomplished will become more apparent in the light of the accompanying disclosure. In at least one embodiment of this invention at least one of the foregoing objects will be achieved.

In accordance with this invention we have provided an alkaline aqueous water base drilling fluid particularly suitable for drilling through a heaving shale formation characterized by a relatively high dissolved barium or barium ion content suflic'ient to effectively stabilize and control the mud-making properties of heaving shale materials or clays in contact with the drilling fluid. More particularly, we have provided an improved alkaline aqueous drilling fluid comprising an alkaline aqueous phase which is substantially saturated with respect to calcium hydroxide and which contains a water-soluble barium compound having a solubility in said aqueous phase greater than that of calcium hydroxide dissolved therein in an amount sufflcient to yield a barium ion concentration in said aqueous phase of at least about 300 parts per million by weight or a total calcium and barium ion content of at least about 500 parts per million by weight. Still in accordance with this invention, We have provided a drilling fluid reagent admixture suitable for the preparation of such a drilling fluid or suitable for the preparation of the alkaline aqueous phase thereof.

A drilling fluid in accordance with the practice of our invention may be prepared in the first instance by'the addition of the drilling fluid reagent admixture of this.

, invention to a water admixture of hydratable clayey material together with the usual, conventional drilling mud additives (water loss additive, weighting material, emulsifying agent and the like), if desired; or a conventional aqueous drilling fluid may be converted (broken over) to a drilling fluid in accordance with our invention by the addition of the reagent admixture disclosed herein or by the separate addition of the various components making up a drilling fluid in accordance with the teachings of this invention.

A characteristic of an aqueous drilling fluid (which may be a water-base fluid, an oil-in-water emulsion fluid) of this invention is the presence therein of an alkaline aqueous phase, usually having a pH not greater than 12.6, usually in the range 11.2-12.5, although it might have a pH corresponding to the pH of a saturated aqueous solution of barium hydroxide, about 13.0. For example, the aqueous phase (filtrate) is saturated with calcium hydroxide and contains a water soluble (solubility greater than that of calcium hydroxide) barium salt dissolved therein; or the aqueous phase may be saturated with calcium hydroxide and contain barium hydroxide dissolved therein. In each instance the aqueous phase is saturated with respect to calcium hydroxide and contains at least about 500 parts per million (p. p. in.) by weight, preferably in the range 650-1500 p. p. m. or higher, of dis solved barium and calcium, either as the barium or calcium ions, per se, or as a barium-containing ion or a calcium containing ion.

The aqueous phase of the drilling fluid is alkaline due to the presence therein of dissolved calcium hydroxide, and sometimes due also to dissolved barium hydroxide, which may be added directly to the drilling fluid either as calcium hydroxide or as hydratable calcium oxide, or barium hydroxide or barium oxide, respectively, or created or otherwise generated in. situ by metathetical reaction between a water-soluble calcium compound, and barium hydroxide, e. g., barium pentahydrate, or by the addition of a water-soluble barium compound which when dissolved in water yields barium hydroxide. If desired, the calcium hydroxide, and barium hydroxide may be generated in situ within the aqueous phase by metathetical reaction involving a calcium salt, such as calcium chloride, and a barium salt, such as barium chloride, preferably in slight excess, and an alkali metal hydroxide such as sodium hydroxide in an amount not greater than the stoichiometric amount with respect to the added calcium and barium salt. In any event it is a characteristic of the alkaline aqueous phase of the drilling fluid of this invention that it is saturated or substantially saturated with respect to calcium hydroxide and in addition contains dissolved barium derived from a water-soluble barium compound, such as barium hydroxide or a barium salt, such that the barium ion concentration in the resulting aqueous phase is at least 300 parts per million by weight, preferably in the range 500-1500 parts per million by weight or higher.

The alkaline aqueous phase found in a drilling fluid in accordance with our invention may be prepared by the addition of lime (calcium hydroxide) and a water-soluble barium salt (barium chloride) to Water; or by the addition of calcium chloride, sodium hydroxide and a watersoluble barium salt (barium chloride) to water; or by the addition of barium hydroxide (barium pentahydrate) and calcium chloride to water; or by the addition of calcium hydroxide and barium hydroxide to water. Preferably, in order to insure that the aqueous phase is saturated with respect to calcium hydroxide, there is present in the drilling fluid in contact with the aqueous phase free, undissolved, solid calcium hydroxide or lime.

Suitable Water-soluble calcium compounds which may be employed in the preparation of an alkaline aqueous drilling fluid in accordance with this invention include such calcium compounds as calcium hydroxide, hydratable lime and such watersoluble calcium salts as calcium acetate,

calcium nitrate, calcium chloride, calcium formate, cal: cium gluconate and calcium citrate. Even calcium sulphate may be employed in the preparation of the alkaline aqueous phase in accordance with this invention but its use is not particularly desirable since if the calcium sulfate is added in excess, it yields sulfate ions which form in the presence of barium ions the water-insoluble barium sulphate thereby tending to reduce or deplete the barium ion content of the aqueous phase.

Water-soluble barium compounds which are useful in the preparation of the aqueous alkaline phase in accordance with this invention include barium hydroxide, barium oxide, barium peroxide, or those barium compounds which yield barium hydroxide when added to water, or the readily water-soluble barium salts, that is, those barium salts which possess a solubility in Water greater than that of calcium hydroxide, e. g., barium chloride, barium nitrate, barium formate, barium acetate, barium propionate. barium butyrate and the like.

As indicated hereinabove, in accordance with one fea ture of this invention there is provided a reagent mixture in liquid form (solution or slurry) or dry solid form which when added to water, which may or may not contain a colloidal hydratable drilling clay, such as a bentonitic type drilling clay therein, provides the desired. alkalinity and/or barium ion content in the aqueous filtrate phase of an aqueous drilling fluid to which the same is added. Such a reagent or additive admixture in accordance with this invention would contain a watersoluble barium compound, such as barium hydroxide or other water-soluble barium compound which upon dinolution in water yields barium hydroxide, or a watersoluble barium salt such as barium chloride, barium nitrate, barium acetate and the like, as well as calcium hydroxide or lime. The weight ratio of such an admixture containing a water-soluble barium compound, web as barium chloride or barium pentahydrate, and a calcium compound which upon addition to water or by reaction with barium hydroxide yields calcium hydroxide, is usually in the range 1:1-6, respectively. Desirably such a reagent admixture would also contain a suitable clay dispersing agent such as a lignosulfonate, e. g., barium lignosulfonate, calcium lignosulfonate, e. g., Kembreak, or sodium lignosulfonate, yellow dextrin which is a water-dispersible degradation product of starch or Indulin A which is a purified pine Wood lignin derived from paper pulp sulphate black liquor and sold under the abovementioned trade name by the West Virginia Pulp and- Paper Company, Inc., such as a three component admixture wherein the barium ion component (BaCl, or

barium pentahydrate), the calcium hydroxide component (lime or CaCl and the clay dispersing component we present in the weight ratio range 0.5-1 :0.5-l0:0.5-10, respectively. It is mentioned, however, that any suitable dispersing agent may be employed in the admixture in accordance with this invention provided, of course, it a compatible with its environment not only within the reagent admixture but also with its enviornment within the drilling mud to which it is added, i. e., it is not salted Out and does'not undergo a chemical reaction or other physical or chemical change which would render it unsuitable or useless as a clay dispersing agent and provided, of course,

it exhibits sufiicient dispersing power in the drillingfluid,

todisperse the hydrated drilling clay material in the usual manner within the drilling fluid. Another suitable dispersing agent is a predominantly sodium salt of a polymeric polyphenol derivative apparently obtained as an extract of hemlock bark and sold under the trade name Rayflo by the Rayonier Company, Inc.

An aqueous drilling fluid prepared in accordance with this invention might also include the usual water 10m. additives such as prehydrolyzed starch commercially available under the trade name Impennex or carboxymethylcellulose (CMC) and the like.

It is pointed out that in an oil-in-water emulsion drill '5 ing fluid prepared in accordance with this invention the Water loss is low as compared with an oil-free water base mud also prepared in accordance with this invention. Presumably the dispersed emulsified oil phase, usually a diesel oil fraction, decreases or inhibits water loss.

tration in the aqueous phase of at least about 300 p. p. m., although a smaller concentration, e. g., barium ion concentration in the range 100-200 p. p. m., might also be useful.

As will be apparent to those skilled in the art many The following tests are illustrative of the practice of alterations, substitutlons and changes may be made withthis invention and the advantages to be obtained in emout departing from the spirit or scope of this invention. ploying a drilling fluid containing an alkaline aqueous We claim: phase saturated with respect to calcium hydroxide and 1. An aqueous drilling flu1d comprising an alkaline having a relatively high dissolved barium ion content. aqueous phase which consists essentially of a saturated In carrying out these tests synthetic heaving or'sloughing aqueous calcium hydroxide solution and a water-soluble shale samples, obtained by slurrying Rogers Lake clay, filbarium compound such that the barium ion concentratering the resulting admixture and aging the resulting tion n said aqueous phase is at least 300 parts per million filter cake, were immersed into 200 cc. portions of an by weight, said aqueous phase having a pH in the range aqueous alkaline solution prepared, as indicated herein- 11.2l3.0. below, in order to demonstrate the advantages of the 2. An aqueous drilling fluid comprising a hydratable practice of this invention. The shale samples were imclayey material dispersed in an alkaline aqueous phase mersed for seven days and after this period their appearwhich consists essentially of a saturated'aqueous calcium ance was noted and the samples were qualitatively tested hydroxide solution and a Water-soluble barium compound for hardness. The results of these tests are set forth in dissolved therein inan amount to yield a barium ion con- Table No. 1. centration in said aqueous phase of at least 300 parts per Table No. I

Versenate Test Composition of aqueous phase Pf Mr cc. Ca and Cl conc pH Physical Hardness No. Ba concenp. p. m Appearance tration 1 1 p. p. b. Barium Pentahydrate r 1.1 1. 2 C-Si) -1 2 2 p. p. b. Barium Pentahydrate 2.0 2.05 OSD -2 3 52 p. p. b. BaClz.2HzO NC-ND-SS -2 4 1al2b]]3ia)O1z.2HzO VSO-ND 0 a 8. 5 pub Bammon Filtered 2.0 .1 C-ND 2 6 Sat. Ga(OH)z (Solution of Test 1 p. p. b. 1.0 1.05 O-ND 2 S No. 5) diluted 1:1.

3 2. 7 }Filtered 2.0 2.1 2.70 1,750 11.9 o-ND 2 s Sat. Ca(0H)1 (Solution of Test 2 p. p. b. 1.0 1.05 1. 875 11.6 C-ND 2 lp.p. arium enay ae 9 {1143 up boa in 0.90 0.95 2.1 1,000 1 .0 G-ND 2 10- 5:? g 0.98 3.17 1,900 12.5 o-ND 2 11 -1 Pentahydmte 0.95 5. 03 3, 550 12. 5 C-ND 2 {5 1. 95 3.1 1, 000 12.9 C-ND 2 13 3 1.10 4.0 1,950 12.9 .C-ND 2 14 1.0 r 5.7 3,500 12.8 CVND 2 disclosure.

P. p. b.=pounds per barrel (42 gals.). P. p. n1.=parts per million b wt Pi is the number of cos. of N/ H S 04 required to titrate 1 cc. to phenolphthalein end point.

Mt is the number of cos. of N /50 H 804 required to titrate 1 cc. to methyl orange and point.

Versenate cc. is the number of cos. of standard Versenate solution required to titrate 1 cc. of the aqueous phase.

Physical appearance: C-cracked; SC-slightly cracked; VS O-very slightly cracked; SS-slightly smoothed; NO-no cracking;

D-dispersed; SD-some dispersion; N Dno dispersion.

persed.

Qualitative hardness scale: 2-hardened; 1slightly hardened; 0no effect;

1-s1ightly softened; 2softened; 3--dis- As indicated by the foregoing test data, see particularly million by weight, said aqueous phase having a pH in the tests 5-14, an alkaline aqueous phase saturated with calcium hydroxide and having a relatively high barium ion concentration effectively stabilizes and hardens a normally dispersing shale. It is this aqueous alkaline phase which is the active and essential component of a drilling fluid prepared in accordance with this invention and which imparts the shale stabilizing properties to the drilling fluid containing the same.

Another feature of this invention is the improvement it imparts to the drilling fluid of the type set forth in our copending patent application Serial No. 484,307, filed January 26, 1955, now abandoned, the disclosures of which are herein incorporated and made a part of this In accordance with this feature it appears that the high temperature gelation properties of the drilling fluid of the above-identified application are improved by the incorporation therein in the aqueous phase of a water-soluble barium compound, such as barium hydroxide or a barium salt such as barium chloride, preferably in an'amount to yield a barium ion concenrange .1 1.2-13 .0.

3. A drilling fluid in accordance with claim 2 wherein the concentration of barium ion in the aqueous phase is in the range 500-1500 parts per million by weight.

4. A water base drilling mud comprising an alkaline aqueous phase, a hydrated drilling clay dispersed in said aqueous phase and a dispersing agent for said clay, said aqueous phase consisting essentially of a saturated aqueous calcium hydroxide solution and a water-soluble barium compound which has a solubility in said aqueous phase greater than thatof calcium hydroxide dissolved therein to yield a barium ion concentration in said aqueous phase of at least 300 parts per million by weight, said aqueous phase having a pH in the range 11.2-13.0.

5. A drilling mud in accordance with claim 4 wherein said dispersing agent is a lignosulfonate.

8. A' drilling mud in accordance with claim 4 wherein said bariumcompound is barium hydroxide.

9. A drilling mud in accordance with claim 4 wherein said barium compound is barium hydroxide and wherein said aqueous phase contains calcium chloride dissolved therein in an amount to form calcium hydroxide in said aqueous phase by metathetical reaction with said barium hydroxide, the amount of calcium hydroxide being formed in .situ being sufficient to saturate said aqueous phase.

10. A drilling mud in accordance with claim 4 wherein said dispersing agent is a sodium salt of a polymeric polyphenol derivative obtained as a hemlock bark extract.

11. An aqueous drilling mud comprising an alkaline aqueous phase and a hydrated drilling clay dispersed in said aqueous phase, said aqueous phase consisting essentially a saturated aqueous solution of calcium hydroxide and a water-soluble barium compound which has a solubility in said aqueous phase greater than that of calcium hydroxide dissolvedtherein to yield a barium ion concentration in said aqueous phase of at least 300 parts per million by weight, said calcium hydroxide having been generated in said aqueous phase by a metathetical reaction by the dissolution in water of a water-soluble calcium salt and barium compound which when added to water yields barium hydroxide, said aqueous phase having-a pH in the range 11.213.0.

12. An aqueous alkaline drilling fluid containing undissolved calcium hydroxide and a dispersing agent for hydrated clayey material and an alkaline aqueous phase containing hydrated drilling clay dispersed therein and consisting essentially a saturated aqueous calcium hydroxide solution and a water-soluble barium compound which has a solubility in said aqueous phase greater than that of calcium hydroxide dissolved therein to yield a barium ion concentration in said aqueous phase of at least 300 parts per million by weight, said drilling fluid containing calcium hydroxide and said dispersing agent in substantially equal amounts by Weight, said aqueous phase having .a pH in the range 11.2-13.0.

13. An aqueous drilling fluid containing a Water-soluble barium salt, calcium hydroxide and a dispersing agent for hydrated drilling clay in the weight ratio 0.51:0.5-

10:0.5-10, respectively, said drilling fluid comprising analkaline aqueous phase having a pH in the range 11.2--

12.6, said aqueous phase consisting, essentially of a saturated aqueous calcium hydroxide solution and a water soluble barium compound dissolved therein to yield a.

barium ion concentration; in. said aqueous phase of at least 300 parts per million by weight.

14. In the drilling of a bore hole through-a heaving shale formation wherein a drilling fluid is passed through the bore hole in contact with the heaving shale fauna-- tion duringthe drilling operation, the improvementwhich comprises contacting said heaving shale formation. with 1 an aqueous drilling fluidcomprising a hydratable clayey material dispersed in an alkaline aqueous phase, said to yield a barium ion concentration of at least 300 per million byweight, said aqueous phasev having. 22H.

in-the range 11.213.0.

15. A drilling mud additive suitable for use in the preparation of an aqueous alkaline drilling fluid useful for drilling through heaving shale consisting essentially of a water-soluble barium compound, calcium hydroxide and a clay dispersing agent in a weight ratio in the range 0.;5 l:0.510:0.5l0, respectively,

16. A drilling mud additive consisting essentially of substantially equal amounts by weight of a water-soluble barium salt which has a solubility in water greater than that of calcium hydroxide, calcium hydroxide and calcium lignosulfonate. 17. A drilling mud additive consisting substantially equal amounts by weight of a water-soluble barium salt which has a solubility in water greater. than that of calcium hydroxide, calcium hydroxide and a clay dispersing agent. 1

References Cited in the file of this. patentv UNITED STATES PATENTS Larkin Dec; 9, 1941 Scotty Aug. 23. 1957 essentially of i 

1. AN AQUEOUS DRILLING FLUID COMPRISING AN ALKALINE AQUEOUS PHASE WHICH CONSISTS ESSENTIALLY OF A SATURATED AQUEOUS CALCIUM HYDROXIDE SOLUTION AND A WATER-SOLUBLE BARIUM COMPOUND SUCH THAT THE BARIUM ION CONCENTRATION IN SAID AQUEOUS PHASE IS AT LEAST 300 PARTS PER MILLION BY WEIGHT, SAID AQUEOUS PHASE HAVING PH IN THE RANGE 11.2-13.0. 